Line lets you sent messages and make calls by using your existing data plan, similar to WhatsApp. Line is hugely popular in regions like Hong Kong, Taiwan, Japan,
Thailand, Singapore. On Android market alone it has been downloaded for over 15 million times. Line by NAVER confirmed just couple of hours ago via their official twitter that the app is already being made for WP.
Windows Phone version is in development
One app Nokia is certainly happy to see on it’s strong market.